DANIEL Tammet really doesn’t want to be known as the “number guy”. It’s a tempting handle to give someone who, with a bit of practice, can recite pi to 22,514 decimal places from memory, can multiply ridiculously large numbers in his head and describes the number six as being cold and dark, “almost like a black hole”. Still, though, Tammet is more than just an incredible mathematical talent.

Does it seem a little absurd to say this, to be at pains to point out that Tammet is more than just a brain, however incredible that brain is? No, I don’t think it is. To be seen as some kind of super computer, for only one aspect of his extraordinary capacity, is limiting. It makes perfect sense that it is a misconception that Tammet is most eager to dispel.

Tammet’s new book, Thinking in Numbers, which follows his bestselling autobiography Born on a Blue Day and his subsequent work, Embracing the Wide Sky, references numbers in the title, but it is a collection of essays on subjects as diverse as Shakespeare and Tolstoy, a rumination on snow and another on chess, as well as a fantastically nuanced piece about his mother. It is a collection which showcases Tammet’s extraordinary talent and, more than that, hints at the direction in which he wants those talents to be focused.

“Mathematics isn’t inimical to imagination,” he says on one of those disconcertingly clear phone lines from his home in Paris. “It’s actually essential to how we understand ourselves, our world, our lives. To think in numbers is to imagine, to imagine all kinds of worlds and possibilities that we haven’t experienced ourselves and that we may never experience. In the way that when we read a novel it transports us and liberates us from a point of view imposed on us by our biology or history or geography.”

Of course, for those of us with a limited understanding of maths, ground out of lessons at school that made little sense or seemed to have little use outside of class, the nuance of Tammet’s argument is demanding. His evident joy in numbers is at times elusive. But he’s persuasive, his elegant writing ensures that.

Tammet is a high-functioning autistic savant, one of maybe 50 in the world. His brain is capable of astonishing feats in languages and mathematics. He has synesthesia, which means that he understands numbers not just as quantities, but as colours, shapes and textures. For Tammet the key to mathematics is imagination, it’s about being able not only to engage with what is around us, but to ponder what might be. His way of exploring this through history and language and literature means his writing defies neat classification as non-fiction. Instead it occupies a liminal position, somewhere between non-fiction and literary prose.

“I was always interested in writing something that’s as close to fiction as possible,” he says. “I wanted to bruise that barrier without breaking it, between non-fiction and fiction, because I think that’s what mathematics can help us to do. It shows us that the boundaries that shape our lives can also hem us in and limit us - but those boundaries are much more malleable and flexible than we are sometimes led to believe. I wanted to take true stories from history – about Shakespeare or Omar Khayyam – and explore them imaginatively.”

By examining numbers in this way, creatively and imaginatively, Tammet is dissolving the dichotomy between mathematics on one hand and art on the other. He’s also resisting the stereotype of a brain such as his being machine-like, a super-powerful computer. Rather, hyperconnected brains such as his (Tammet believes a series of seizures when he was a small boy rewired the circuitry of his brain) are the very antithesis of “coolly calculating machines”; instead they create a “beautiful, swirling chaos” that draws information from all over the brain to arrive at their conclusions.

“One of the misconceptions that I could suffer from being a writer on the autistic spectrum, albeit on the high-functioning side, is that I’m a numbers guy who doesn’t understand emotion or people or language,” he says. “It’s true that I had difficulties in all of those areas and where I am now took a very complicated journey, more complicated than that of an Ian McEwan or a Margaret Atwood, but in the end, who’s not to say that a high-functioning autistic author couldn’t write prose of that quality one day?”

Who indeed? The bestselling Born on a Blue Day established Tammet as a writer of unique capabilities. It also had a profound impact on Tammet, 33. Published in 2006, the book marked “a sea change” in his life. In exploring his experience of growing up it gave readers a fascinating window into his unique sense of the world, but it also allowed him to develop a new perspective on who he is and who he can be.

When the book was published, Tammet was 26 and living in a small seaside town in Kent. It was, he says, a very restricted way of life. “I hardly ever went out. I hardly ever travelled. I was happy in a sense but it was a very restricted happiness that I imposed on myself in order to control my condition and the symptoms. Born on a Blue Day allowed me to realise what I was capable of was not simply remembering information or such and such but that there was a kind of sensibility, a sensitivity that was more reminiscent of writers than mathematicians in the sense of people think of them.”

There is no doubt that part of what motivates Tammet is dispelling misconceptions about autistic people and savants but also, there is a sense that he is on his own journey, following the process of his own evolution as he revises and expands his capacity, not just his brain power but who he is as a man. It’s a process he can trace in his relationship with books and literature.

As a child, the books he loved were encyclopedias in which he found definitions and lists of capitals, population figures and climate information. Data he could mine and hoard. Gradually, though, his reading evolved and he was drawn to biographies and history. Still information heavy, these gave him a more personal perspective on events and places. By the time he was 18 or 19 he had moved on to poetry, getting a further, more intimate insight into what it is to be human, to want, as he puts it, “to connect with others, to be understood by someone who isn’t like you”. It’s a process of evolution that is paralleled in his development as a writer.

There is something genuinely moving about Tammet’s understanding of the central importance in our human experience of connection with others. Perhaps it’s that he approaches it from the perspective of someone for whom it didn’t come naturally, but which because of his autism, was a skill which had to be learned and trained through practice. Numbers were once a refuge for Tammet from the teasing he experienced at school for being different, now he is using his unique gifts to offer them and the potential they can reveal to those of us who lack his innate mathematical ability. It seems to me a profoundly generous undertaking.

Happily settled in Paris with his partner, photographer Jerome Tabet, there is a sense that Tammet is just getting a sense of his real capacity. He thinks it’s likely that he’ll take French nationality when he has the opportunity later this year, having lived in the country for five years. He’s at ease there – his books, although translated into more than 20 languages, work best, he says, in French. Tammet’s explanation is that in France the division between mathematics and literature doesn’t exist in the same way as it does in Britain or America. To say that you’re a writer in France is, he says, “almost wonderful”. It’s not that he’s dissing Britain. Why would he? His family (he is the eldest of nine) is here and London isn’t far for when he visits. But Paris is home.

“I feel totally at ease in both worlds and I think that’s a nice way of thinking about how I’ve got one foot in the world of numbers and one in the world of language and literature,” he says. “I’m very comfortable with that complexity.”

CLAIRE BLACK

• Thinking in Numbers is published by Hodder & Stoughton on Thursday 16 August, £18.99. Daniel is appearing at the Edinburgh International Book Festival on Wednesday 15 August, 3:30pm-4:30pm, £10 (£8), www.edbookfest.co.uk and Thinking in Numbers will be BBC Radio 4’s Book Of The Week from Monday 20 August, www.bbc.co.uk